This invention relates generally to light sources and particularly to light sources suitable for forming counter propagating waves in the sensing loop of a fiber optic rotation sensor. Still more particularly, this invention relates to a light source formed in a glass waveguide for use in a fiber optic rotation sensor.
A fiber optic ring interferometer typically comprises a loop of fiber optic material that guides counter-propagating light waves. The light waves typically originate in a solid state optical source such as a superluminescent diode. Rotation of the loop creates a relative phase difference between the counter-propagating waves by the well known Sagnac effect. The amount of phase difference is a function of the angular velocity of the loop. After traversing the loop, the counter-propagating waves combine so that they constructively or destructively interfere to form an optical output signal.
The output signal produced by the interference of the counter-propagating waves varies in intensity as a function of the rotation rate of the loop. Rotation sensing is accomplished by detecting the optical output signal and processing it to determine the rotation rate.
Superluminescent diodes are the light sources in some rotation sensing systems. Superluminescent diodes provide light having the desired broad bandwidth. However, superluminescent diodes are expensive and have operating lifetimes that are too short for use in many navigating systems. A triaxial gyro for measuring rotations about three mutually perpendicular axes as required for navigation may include three SLD light sources. A triaxial gyro may also include a plurality of optical couplers arranged to divide the light output from a single SLD source to provide three separate beams. Both of these approaches for providing suitable light beams for a triaxial gyro are expensive and do not solve the short lifetime problem associated with SLDs.